Six months after apprehending methodical killer Sage Wellington, FBI Agent Sidney Stone receives mysterious DNA test results revealing a half-sister she never knew existed – just as a series of deaths bearing Wellington's distinctive signature begin to surface, forcing Sidney to confront the possibility that her newfound family connection may be hiding deadly secrets.

When a package containing DNA test results arrives unexpectedly at Sidney Stone's desk, the discovery of a half-sister should be cause for celebration. Instead, it marks the beginning of a dangerous game.

As Sidney investigates her connection to her half-sister, forensic psychologist Naomi White, a chilling series of "accidental" deaths echoing Sage Wellington's methodology demands her attention. The victims share a disturbing pattern – all dismissed trauma victims' experiences. With each new death, evidence increasingly points toward Naomi, whose professional expertise mirrors Sidney's own unsettling ability to understand killers.

As Sidney searches for her long-absent father for answers, she must determine whether Naomi is a fellow pawn in someone's elaborate scheme or the mastermind herself. Family ties have never been more dangerous, and Sidney's intuition – the very skill that makes her exceptional – may be clouded by a longing for connection she's denied herself since childhood.